Electronic conditioning of gaseous discharge display panels

ABSTRACT

There is disclosed a method and apparatus for electronic conditioning of gaseous discharge display panels particularly of the type disclosed in Baker et al. U.S. Pat. No. 3,499,167 and Bitzer et al. U.S. Pat. No. 3,559,190. Electronic conditioning is achieved by periodically causing unstable discharges in the panel particularly at all sites which are not in the on state. This is achieved by applying an increased amplitude sustainer pulse at regular intervals not exceeding about 200 microseconds between pulses. By applying larger magnitude pulses which are above the firing voltage but below the voltage level required to turn a cell &#39;&#39;&#39;&#39;on&#39;&#39;&#39;&#39;, the discharge sites in the panel are conditioned for uniform operation.

United States Patent [1 1 Petty et al.

[451 Sept. 3, 1974 1 ELECTRONIC CONDITIONING OF GASEOUS DISCHARGE DISPLAY PANELS [75] Inventors: William D. Petty, Perrysburg, Ohio;

J. Kirkwood H. Rough, Riverside,

Calif.

[73] Assignee: Owens-Illinois, Inc., Toledo, Ohio [22] Filed: Mar. 31, 1972 [21] Appl. No.: 240,022

Primary ExaminerI-lerman Karl Saalbach Assistant Examiner-Lawrence J. Dahl Attorney, Agent, or Firm-Donald Keith Wedding [57] ABSTRACT There is disclosed a method and apparatus for electronic conditioning of gaseous discharge display panels particularly of the type disclosed in Baker et al. US. Pat. No. 3,499,167 and Bitzer et al. US. Pat. No. 3,559,190. Electronic conditioning is achieved by periodically causing unstable discharges in the panel particularly at all sites which are not in the on state. This is achieved by applying an increased amplitude sustainer pulse at regular intervals not exceeding about 200 microseconds between pulses. By applying larger magnitude pulses which are above the firing voltage but below the voltage level required to turn a cell on, the discharge sites in the panel are conditioned for uniform operation.

2 Claims, 2 Drawing Figures PANEL /0 (BAKER ET AL u. s. PATENT 3,49936'7) MULT/PLEX ADDRESSING C l/EC U/TS MULTIPLE X ADDRESSING C [RC 0/ T5 DATA 8 CON TROL SUS TA/NER CONTROL x a CONDITIONER V PATENTEB 3 I974 MUL T/PLE X ADDRESSING CIRCUITS MUL T/ PL EX ADDRESS/N6 CIRCUITS 0118734 CONTROL v 26 SUS TA/NER CONTROL 8 C OND/ TIONE' R f-susTA/NE/a I CYCLE I 7 ELECTRONIC CONDITIONING OF GASEOUS DISCHARGE DISPLAY PANELS BACKGROUND OF THE INVENTION Gaseous discharge display/memory panels of the type to which the present invention are pertained are disclosed in Baker et al. US. Pat. No. 3,499,167 and in Bitzer et al. US. Pat. No. 3,559,190. In such panels the gaseous medium is conditioned (e.g. provided with a supply of charges such as electron or other particles in the discharge gaps) for the ionization process by the application of firing potential to border discharge sites and maintaining the border discharge sites in an on state so that, as in the case of the Baker et al. patent, open photonic communication of photonic energy between discharge sites at the border areas to discharge sites interior of the panel can condition the discharge sites in the display/data storage areas of the panel for operation at relatively uniform firing potentials. Alternatively, the gas may be conditioned by providing exterior sources of ultraviolet radiation, or by placing a radioactive material in the space or in the glass forming the structure. There are a number of other expedients to conditioning the gas for suitable operation and these fall into the category of conditioning by panel construction generally.

There is another category or classification of conditioning, namely, electronic conditioning. For example, in one prior electronic conditioning arrangement, a preaddress pulse is applied to a series of intermediate units which connect at least one pilot discharge unit to at least one discharge unit to be addressed so as to propigate the conditioning of the gaseous medium across the panel. In another situation, electronic conditioning utilizing a grid is proposed. In still another other group of techniques (as, for example, disclosed in the Bitzer et al. patent), the gas (a neon-nitrogen gas mixture) is conditioned by applying a conditioning pulse having a pulse width of about 2 microseconds to all conductors every one hundred to two hundred microseconds. The present invention is an improvement on this technique. In accordance with the present invention, periodically, a normal sustainer pulse voltage, preferably having a square waveform, is given a slightly greater amplitude. Thus, according to the invention, a standard square wave sustainer voltage waveform is applied to the panel with the sustainer signal being capable of the supporting normal bistable operation of the panel while at selected time intervals, larger amplitude pulses which are above the firing voltage level are applied to cause a discharge over the entire panel. However, this magnitude of voltage is selected to be only slightly greater than the firing voltage so that there is a minimum resultant wall voltage which, in any case, will not be sufficiently large to result in a stable sequence of discharges with the continued application of the sustaining signal, and the discharge will die out. That is to say the memory property of the panel is purposely not established even though a discharge has occurred.

Improvement in the present invention as compared with present techniques of maintaining the border sites on, or other forms of electronic conditioning, reduces power consumption with little degradation in display contrast in the panel.

The above and other objects and advantages and features of the invention will become apparent from the following specification and the attached drawings wherein:

FIG. 1 is a schematic diagram of a gaseous discharge panel and circuitry for operating same, and

FIGS. 2A, 2B, and 2C are wave form diagrams used to explain the principle of operation of the invention; FIG. 2A being the sustainer voltage wave form as applied to the X or row conductors, FIG. 28 being the sustainer voltage wave form as applied to the Y or column conductors and FIG. 2C being the relative differ ence voltage as applied to the gas, being the voltage dif ference between voltage wave form of FIG. 2A and a waveform in FIG. 2B.

' Referring now to FIG. 1 of the drawing, a typical gaseous discharge panel such as is disclosed in Baker et al. US. Pat. No. 3,499,] 67 is constituted by a pair of support plates 11 and 12, with the row conductor array 13 being on a row plate 12 and the column conductors 13 being on column plate 11. These conductor arrays in the operating or viewing area V of the panel have a thin dielectric coating applied thereto and the plates are joined in spaced apart relation by a spacer sealant member 16. It will be appreciated that the panel may be constructed in accordance with the teachings of Bitzer et al. US. Pat. No. 3,559,190.

Panels as disclosed in these patents have an electrical memory constituted by the storage of charges produced by discharge on one or more dielectric surfaces (not shown) in contact with the gas. Thus, the conductors are non-conductively coupled to the gas. As described above, the conductors in arrays 13 and 14 form a cross conductor matrix wherein the discharge sites are arrayed in columns and rows. The ionizable gaseous discharge medium is typically a mixture of two gases at a selected pressure and is confined the thin gaseous chamber therebetween. A very useful gas composition is a Neon-argon gas mixture as disclosed in Nolan application Ser. No. 764,577 filed Oct. 2, 1968. The dielectric layer prevents the passage of any conductive current from the matrix conductor member to the gaseous medium and also serves as the collecting surfaces for discharges in the ionizable gaseous medium during alternate half-cycles of the periodic operating potentials applied thereto. In addition to the above improved panel structures, further improvements have been achieved by including a dielectric or insulative overcoating (not shown) on the dielectric coating of the aforementioned Baker et al. patent, the overcoating being of a lead oxide composition (for example) as taught in Ernsthausen US. Pat. No. 3,634,719. Typically, the discharge gap in such panels is selected to be between 4 and 6 mils and is usually under 10 mils. In such panel structures a typical sustainer voltage applied to a conductor may be a square wave of 40 to 50 KHz and of about volts (VSS).

In a typical panel, the row conductors may be spaced very close together as, for example, on 20-30 mil centers and, in like manner, the column conductors may be spaced on the same spacing or a difference in spacing may be used if desired. In FIG. 1, all the row conductors 13 of an array are shown as being served from the same side or edge of plate 12 but it will be apparent that due to the large number of conductors and being closely spaced on the plates, the conductors may be served from opposite ends in alternate fashion as disclosed in Hoehn US. Pat. No. 3,631,287, including the angulation and grouping thereof if desired.

The addressing circuits 18 for the row conductors and the addressing circuits 19 for the column conductors may be multiplex resistor-diode addressing matrices or individual addressing or pulsing circuits for each row or column conductor with the timing of the addressing (write and erase) pulses being in accordance with the teachings of Johnson et al. US. Pat. No. 3,618,071. The multiplex matrix-type selection circuit may be of the type disclosed in Leuck application Ser. No. 135,021 filed Apr. 19, 1971, now U.S. Pat. No. 3,365,400. Such matrix circuits float upon their respective sustainer sources 22 and 23, respectively, it being noted that the sustainer generators 22 and 23 have a common point of reference potential SG. The addressing circuits 18 and 19 are controlled by signals from data source and control circuit 25 which also may control sustainer generators 22 and 23 in their timing (the connection not being shown).

The above describes in general the environment or setting of the present invention which is concerned with the conditioning of all of the discharge in the panel for operation at relatively uniform potential, e.g. the provision in each discharge gap of charged particles for initiating discharge sequences on the application of information bearing firing signals to selected conductors in the array.

In FIG. 1 there is shown a block 26 labelled sustainer control and conditioning which, as indicated above may be part of data and control circuit 25 but is shown as a separate block in FIG. 1 for clarity of explanation and delineation of the present invention from the art. Thus, the sustainer generator, (row sources 22 and column source 23) may be of the type shown in FIG. 6 of Miavecz et al. application Ser. No. 21 1,371, filed Feb. 23, 1972 and entitled Electrical Supply System and Method for Improving the Operating Characteristics of Gaseous Discharge Display Panels as well as in the sustaining generator disclosed in the application of David S. Wojcik entitled Baker Clamped Sustainer Voltage Generator for Pulsing Discharge Display Panel Ser. No. 210,864 filed Dec. 23, 1971.

The waveform of the output voltage from sustainer generator 22 is at the sustainer voltage level VSS (of about 150 volt level) and at about a 4050 KHz pulse rate. It will be noted that each of the voltage pulses V V V V et seq., are at the VSS level whereas the conditioning voltage pulse which is a larger sustainer voltage pulse of a magnitude larger than the normal sustainer voltage VSS but small enough such that there is insufficient charge storage due to the discharge caused by this additional pulse level VC to cause the cell to transfer into the ON state. In other words, the memory property of the panel is not used or established even though a discharge has occurred. In like manner, the sustainer voltage VY has each of its voltage pulses V V V, etc. at the normal sustainer voltage level VSS of about 150 volts. The voltage VCY is, like the voltage VCX, significantly larger than the normal sustainer level but is not large enough to cause a discharge of such intensity as to create sufficient charges stored on the wall to turn the cell ON, so that on the next applied sustainer voltage, there may be wall voltage of a magnitude sufficient, when added to that next succeeding sustainer voltage, to create a further discharge which is less intense than that produced by VCY. In other words, the discharge, in the context of the present invention, results in an unstable discharge sequence"; the applied sustainer voltage is selected to be greater than the normal sustainer voltage to fire all discharge sites but with a resultant wall voltage not being sufficiently large to result in a stable sequence with the application of the next succeeding sustaining voltage pulse. Therefore, the discharges (due to the VCX and VCY voltage pulses) will die out and not be sustained due to the absence of sufficient wall charge. The time interval between the sustaining voltage pulse VCX and the sustaining voltage pulse VCY should not be greater than about 200 microseconds. Improved operation of the panel is achieved therefore by causing each site in the panel to be tired at regular intervals (not exceeding the 200 microseconds mentioned above), so as to thereby condition all of the sites in the panel for uniform operation. This conditioning process, using as it does the sustainer voltage in its uninterrupted form permits user of sustainer voltage generation with the addition of a voltage to constitute the VC voltage level. Thus, the invention is based primarily on the use of the sustainer for electronic conditioning purposes by increasing the level or amplitude of the square wave sustainer at periodic intervals to cause an unstable discharge sequence at these intervals at all sites in the panel which are not in an ON" condition.

Although the invention has been described in its preferred end form, it is clear that the basic principle thereof is applicable by the embodiment obvious to those skilled in the art and it is intended that the claims encompass such obvious embodiments.

What is claimed is:

1. In a method of electronically conditioning the discharge sites in a gaseous discharge display panel of the type having a pair of transverse conductor arrays nonconductively coupled to a thin gaseous discharge medium in said panel and defining a plurality of matrix crosspoints, each said crosspoints locating a discharge site in the panel, and periodic sustainer voltage pulses are applied to all sites, said panel having an internal memory constituted by charges stored therein at said sites resulting in a stable discharge when said sites are in an ON state, and a lack of stable discharge sequence in the OFF state, such that said sites are bistable in operation, said ON state being generated by application of addressing voltage pulses to said sustainer voltage, and wherein all sites in said panel are electronically conditioned by being fired at regular intervals not exceeding about 200 microseconds, the improvement in said electronic conditioning process which comprises said sustainer voltage pulses applied to all sites being of a magnitude to support said bistable operation thereat, respectively, and at said regular intervals causing said sustainer voltage pulses to be sufficiently larger than the magnitude of voltage which supports said bistable operations and cause a discharge at all sites in the entire panel served by said sustainer voltage but only slightly greater than the firing voltage so that the resultant wall voltage will not be sufficiently large to result in the change of any site in the OFF state to the ON state with the application of the succeeding sustaining signal voltage pulses.

array at intervals no greater than about 200 microseconds, the increased amplitude level VC of said sustainer voltage at said interval being sufficient to create unstable discharge sequences at all discharge sites receiving said increased amplitude square wave sustainer voltage pulses, and said increased amplitude level VC being below an amplitude level which would result in said internal memory being established at such sites in the absence of a write voltage pulse. 

1. In a method of electronically conditioning the discharge sites in a gaseous discharge display panel of the type having a pair of transverse conductor arrays non-conductively coupled to a thin gaseous discharge medium in said panel and defining a plurality of matrix crosspoints, each said crosspoints locating a discharge site in the panel, and periodic sustainer voltage pulses are applied to all sites, said panel having an internal memory constituted by charges stored therein at said sites resulting in a stable discharge when said sites are in an ''''ON'''' state, and a lack of stable discharge sequence in the ''''OFF'''' state, such that said sites are bistable in operation, said ''''ON'''' state being generated by application of addressing voltage pulses to said sustainer voltage, and wherein all sites in said panel are electronically conditioned by being fired at regular intervals not exceeding about 200 microseconds, the improvement in said electronic conditioning process which comprises said sustainer voltage pulses applied to all sites being of a magnitude to support said bistable operation thereat, respectively, and at said regular intervals causing said sustainer voltage pulses to be sufficiently larger than the magnitude of voltage which supports said bistable operations and cause a discharge at all sites in the entire panel served by said sustainer voltage but only slightly greater than the firing voltage so that the resultant wall voltage will not be sufficiently large to result in the change of any site in the ''''OFF'''' state to the ''''ON'''' state with the application of the succeeding sustaining signal voltage pulses.
 2. In a gaseous discharge display panel having row-column conductor arrays non-conductively coupled to a gaseous discharge medium in a thin chamber space between said row and said column conductor arrays and means for continuously supplying a periodic square wave sustainer voltage VSS and write/erase voltages, algebraically added to said square wave sustainer voltage to said panel, improvement in electronically conditioning said panel which comprises, means for periodically increasing the amplitude level of at least a portion of the said square wave sustainer voltage as applied to all conductors in said array at intervals no greater than about 200 microseconds, the increased amplitude level VC of said sustainer voltage at said interval being sufficient to create unstable discharge sequences at all discharge sites receiving said increased amplitude square wave sustainer voltage pulses, and said increased amplitude level VC being below an amplitude level which would result in said internal memory being established at such sites in the absence of a write voltage pulse. 